Corynebacteria are commensal bacteria constituting a group which is heterogeneous from the morphological, taxonomic, pathogenic and therapeutic standpoints. This heterogeneity was, for a long time, responsible for a lack of knowledge of this group and limited the identification of the different strains. In man, the pathogenicity of the species belonging to the genus Corynebacterium is very variable, and many corynebacteria form part of the normal flora of the skin and the mucosae. Thus, from a pathological standpoint, some strains are highly pathogenic for man (Corynebacterium diphtheriae), but most are opportunistic bacteria responsible for infections in immunosuppressed or weakened patients. In effect, from an epidemiological point of view, the pathogenic power of corynebacteria was for a long time limited to diphtheria (Corynebacterium diphtheriae), but this disease is currently on the decline on account, in particular, of obligatory vaccination measures, and has given way to new pathologies associated with the advances in hospital medicine. Thus, corynebacteria are more and more frequently isolated in the context of nosocomial infections.
Since these infections caused by corynebacteria (see table below) occur essentially in greatly weakened patients, it is important to have at one's disposal a bacteriological diagnostic test which is sufficiently specific and sensitive to permit a rapid and selective detection of the species responsible, so as to implement a suitable therapy as quickly as possible. Now, at the resent time, analytical laboratories have at their disposal only biochemical and bacteriological tests limited by steps of isolation and of bacterial culture which are essential to the tests, and which are often not sufficiently specific and sensitive to diagnose the presence of a particular species of corynebacteria, and more especially of a pathogenic species, in a biological sample.